RFID

#include <SPI.h>

#include <MFRC522.h>



#define SS_PIN 10

#define RST_PIN 9



MFRC522 mfrc522(SS_PIN, RST_PIN);

MFRC522::MIFARE_Key key;



int block=2;



byte blockcontent[16] = {"Last-Minute-Engg"};
//byte blockcontent[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};


byte readbackblock[18];



void setup()

{

    Serial.begin(9600);
    SPI.begin();

    mfrc522.PCD_Init();
    Serial.println("Scan a MIFARE Classic card");





  for (byte i = 0; i < 6; i++) {

    key.keyByte[i] = 0xFF;  //keyByte is defined in the "MIFARE_Key" 'struct' definition in the .h file of the library

  }

}



void loop()

{


  if ( ! mfrc522.PICC_IsNewCardPresent()) {

    return;

  }




  if ( ! mfrc522.PICC_ReadCardSerial())

  {

    return;

  }

    Serial.println("card selected");




   writeBlock(block, blockcontent);




   readBlock(block, readbackblock);




   Serial.print("read block: ");

   for (int j=0 ; j<16 ; j++)

   {

     Serial.write (readbackblock[j]);

   }

   Serial.println("");

}




int writeBlock(int blockNumber, byte arrayAddress[])

{


  int largestModulo4Number=blockNumber/4*4;

  int trailerBlock=largestModulo4Number+3;

  if (blockNumber > 2 && (blockNumber+1)%4 == 0){Serial.print(blockNumber);Serial.println(" is a trailer block:");return 2;}

  Serial.print(blockNumber);

  Serial.println(" is a data block:");



  byte status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, trailerBlock, &key, &(mfrc522.uid));

  if (status != MFRC522::STATUS_OK) {

         Serial.print("PCD_Authenticate() failed: ");

         Serial.println(mfrc522.GetStatusCodeName(status));

         return 3;//return "3" as error message

  }




  status = mfrc522.MIFARE_Write(blockNumber, arrayAddress, 16);



  if (status != MFRC522::STATUS_OK) {

           Serial.print("MIFARE_Write() failed: ");

           Serial.println(mfrc522.GetStatusCodeName(status));

           return 4;//return "4" as error message

  }

  Serial.println("block was written");

}




int readBlock(int blockNumber, byte arrayAddress[])

{

  int largestModulo4Number=blockNumber/4*4;

  int trailerBlock=largestModulo4Number+3;//determine trailer block for the sector




  byte status = mfrc522.PCD_Authenticate(MFRC522::PICC_CMD_MF_AUTH_KEY_A, trailerBlock, &key, &(mfrc522.uid));



  if (status != MFRC522::STATUS_OK) {

         Serial.print("PCD_Authenticate() failed (read): ");

         Serial.println(mfrc522.GetStatusCodeName(status));

         return 3;//return "3" as error message

  }




byte buffersize = 18;
status = mfrc522.MIFARE_Read(blockNumber, arrayAddress, &buffersize);

  if (status != MFRC522::STATUS_OK) {

          Serial.print("MIFARE_read() failed: ");

          Serial.println(mfrc522.GetStatusCodeName(status));

          return 4;//return "4" as error message

  }

  Serial.println("block was read");

}